Computer systems are becoming increasingly pervasive in our society, including everything from small handheld electronic devices, such as personal data assistants and cellular phones, to application-specific electronic devices, such as set-top boxes, digital cameras, and other consumer electronics, to medium-sized mobile systems such as notebook, sub-notebook, and tablet computers, to desktop systems, workstations, and servers. Computer systems typically include one or more processors. A processor may manipulate and control the flow of data in a computer. To provide more powerful computer systems for consumers, processor designers strive to continually increase the operating speed of the processor. Unfortunately, as processor speed increases, the power consumed by the processor tends to increase as well. Historically, the power consumed by a computer system has been limited by two factors. First, as power consumption increases, the computer tends to run hotter, leading to thermal dissipation problems. Second, the power consumed by a computer system may tax the limits of the power supply used to keep the system operational, reducing battery life in mobile systems and diminishing reliability while increasing cost in larger systems.
One approach to reducing overall power consumption of a computer system is to change the focus of power reduction from the processor to other components that have a significant impact on power. For example, display screens of computer systems typically consume a significant amount of power. For many backlit liquid crystal display (LCD) screens, increasing the brightness of the display screen typically increases its power consumption, and decreasing the brightness of the display screen typically decreases its power consumption. Therefore, it is generally in a user's best interest to lower the average brightness of the display screen over time.